The present application is a continuation of International Application No. PCT/SE04/00857, filed Jun. 2, 2004, which claims priority of SE 0301617-7, filed Jun. 4, 2003, and SE 0301828-0, filed Jun. 19, 2003, all three of which are incorporated by reference.
The present invention relates to a rotatable tool and a blank.
It is previously known through for example WO 98/28455 to press material powder, such as tungsten carbide (WC) together with cobalt (Co), between a punch and a die, and subsequently to sinter the material such that the binder metal is melted and binds the carbides to form tool material for chip removing machining. The known technique brings about a plurality of drawbacks. The powder give off dust and the formed green body (pressed but not sintered material) will not endure handling to any degree. Furthermore the chip flutes must be ground and the method requires time and energy. The problems have partly been solved by injection moulding of cemented carbide mixed in a carrier such as indicated in SE-B-9501687-9. The method of injection moulding brings a high degree of freedom concerning geometry but brings costly investments in moulds.
It is previously known through for example U.S. Pat. No. 4,779,440 and WO/0074870 to form a blank for a helix drill. The extruded blank has chip flutes with uniform pitch along the circumference of the blank.
It is desirable to provide a rotatable tool and a blank having varying pitch of the flush channels.
It is desirable to provide a tool having flush channels of varying pitch.
It is desirable to provide a tool having good durability.
According to an aspect of the invention, a rotatable tool is provided, the tool being made of cemented carbide and comprising a shank for mounting in a rotatable spindle, at least one chip flute, a cutting edge formed at a line of intersection between the at least one chip flute and clearance surfaces at a cutting end of the tool, and at least one flush channel extending through the tool to transfer flushing medium to the cutting end of the tool, wherein the flush channel has a varying pitch.
According to another aspect of the invention, a blank for a tool for chip removing machining is provided, the blank being made of solid cemented carbide and comprising at least one space for forming at least one flush channel in the tool, the space extending through the entire blank, wherein the space has a varying pitch.